Multi-SIM (subscriber identification module) wireless devices have become increasing popular because of the versatility that they provide, particularly in countries where there are many service providers. For example, dual-SIM wireless devices may allow a user to implement two different plans or service providers, with separate numbers and bills, on the same device (e.g., business account and personal account). Also, during travel, users can obtain local SIM cards and pay local call rates in the destination country. By using multiple SIMs, a user may take advantage of different pricing plans and save on mobile data usage.
In various types of multi-SIM wireless communication devices, each modem stack associated with a subscription may store information provisioned by its respective network operator in a SIM, which may allow the SIM to support use of various different communication services. For example, various wireless networks may be configured to handle different types of data, use different communication modes, implement different radio access technologies, etc.
One type of multi-SIM wireless device, referred to as a dual-SIM dual active (DSDA) device, allows simultaneous active connections with the networks corresponding to two SIMs using separate transmit/receive chains associated with each SIM. Such separate components may provide convenience to a user, but may require high power consumption during operation. Another type of multi-SIM wireless device, referred to as a dual-SIM dual standby (DSDS) device, typically provides for a “standby” mode (i.e., idle mode) in which services associated with either SIM may originate or terminate a communication (e.g., a voice call or data call), and in which services associated with both SIMs may receive pages using a shared radio resource. By sharing a radio resource between the services enabled by both SIMs, a DSDS device may allow for a longer battery life than that of a DSDA device, as well as other benefits (e.g., lower cost of the device, avoiding receiver desense from co-located radios, etc.).
However, a disadvantage of sharing a radio resource between services enabled by two SIMs on the same device is that once a service enabled by one SIM registers on a selected network, that service may begin active communications and occupy use of the radio resource to the exclusion of services enabled on other SIMs. In particular, a service enabled by another SIM may be unable to perform initial carrier channel acquisition and signal strength measurements, and therefore be prevented from camping to a cell and registering in a selected network until a tune away period or termination of the active communication.